1. Field of the Invention
The present invention relates to a heat pump type hot water supply apparatus, and particularly to a heat pump type hot water supply apparatus which can perform an air conditioning operation and a hot water supplying operation with energy saving.
2. Description of the Related Art
A conventional heat pump type hot water supply apparatus is generally designed so that a heat exchanger of a hot water supply unit and an outdoor heat exchanger are arranged in parallel in a refrigerant circuit, and under cooling operation refrigerant circulating in the refrigerant circuit is cooled and condensed in both the heat exchanger of the hot water supply unit and the outdoor heat exchanger to cool the room.
FIG. 1 shows a conventional heat pump type hot water supply apparatus 10 (disclosed in JP-A-10-288420, for example). The heat pump type hot water supply apparatus 10 shown in FIG. 1 contains an outdoor unit 12, indoor units 14a and 14b and a hot water stock tank unit 50. The outdoor unit 12 includes a compressor 16, a four-way valve 52 connected to the refrigerant discharge side of the compressor 16, an outdoor heat exchanger 22 connected to the four-way valve 52 at one end thereof, and a first expansion valve 24 connected to the other end of the outdoor heat exchanger 22 at one end thereof. Each indoor unit 14a (14b) includes a second expansion valve 36a (36b) and an indoor heat exchanger 38a (38b). The second expansion valve 36a (36b) is connected to the first expansion valve 24, and the indoor heat exchanger 38a (38b) is connected to the four-wave valve 52.
Furthermore, a first electromagnetic valve 54 is equipped between the compressor 16 and the four-way valve 52, and the hot water stock tank unit 50 is disposed in a passage which extends so as to branch off a refrigerant pipe between the compressor 16 and the first electromagnetic valve 54 and link to the refrigerant pipe between the first expansion valve 24 and the second expansion valve 35a (36b). A third expansion valve 56 is equipped at the refrigerant outlet port of the hot water stock tank unit 50. That is, the hot water stock tank unit 50 is connected to the outdoor heat exchanger 22 in parallel in the refrigerant circuit.
When only cooling operation is carried out in the construction shown in FIG. 1, after the four-way valve 52 is switched as indicated by a solid line, the first expansion valve 24 is fully opened, and the second expansion valves 36a, 36b are opened at predetermined valve opening degrees. In addition, the third expansion valve 56 is fully closed, and the first electromagnetic valve 54 is opened. Under this state, the refrigerant discharged from the compressor 16 is circulated through the outdoor heat exchanger 22, the first expansion valve 24, the second expansion valves 36a, 36b, the indoor heat exchangers 38a, 38b and the accumulator 44 in this order.
On the other hand, when only heating operation is carried out, after the four-way valve 52 is switched as indicated by a broken line, the first expansion valve 24 is fully opened, and the second expansion valves 36a, 36b are opened at predetermined opening degrees. In addition, the third expansion valve 56 is fully closed, and the first electromagnetic valve 54 is opened. Under this state, the refrigerant discharged from the compressor 16 is circulated through the indoor heat exchangers 38a, 38b, the second expansion valves 36a, 36b, the first expansion valve 24, the outdoor heat exchanger 22 and the accumulator 44 in this order.
Furthermore, when hot-water supply operation is needed, the four-way valve 52 is switched as indicated by the broken line, the first expansion valve 24 is fully opened, the second expansion valves 36a, 36b are fully closed, the third expansion valve 56 is opened at a predetermined degree. The first electromagnetic valve 54 is closed, and the refrigerant discharged from the compressor 54 is circulated through a hot-water supply heat exchanger 58 of the hot water stock tank unit 50, the third expansion valve 56, the first expansion valve 24, the outdoor heat exchanger 22 and the accumulator 44 in this order. The refrigerant thus circulated is condensed in the hot-water supply heat exchanger 58, and evaporated in the outdoor heat exchanger 22, thereby enabling the hot water supply operation.
In the conventional heat pump type hot water supply apparatus described above, however, when both the cooling operation and the hot water supply operation or both the heating operation and the hot water supply operation are required to be carried out simultaneously, the refrigerant must be branched to two ways because the hot-water supply heat exchanger and the outdoor heat exchanger are arranged in parallel in the refrigerant circuit, resulting in reduction in efficiency. Furthermore, under cooling operation, the outdoor heat exchanger must be driven at all times.